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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 75 |
| 4 | 621 |
| 5 | 5139 |
| 6 | 42525 |
| 7 | 351891 |
| 8 | 2911869 |
| 9 | 24095475 |
| 10 | 199388061 |
| 11 | 1649919699 |
| 12 | 13652948925 |
| 13 | 112977022131 |
| 14 | 934875505629 |
| 15 | 7736017417875 |
| 16 | 64014903727101 |
| 17 | 529718029036659 |
| 18 | 4383372838967325 |
| 19 | 36272047376485971 |
| 20 | 300148189354569789 |
| 21 | 2483701419932212275 |
[0,1,9,75,621,5139,42525,351891,2911869,24095475, 199388061,1649919699,13652948925,112977022131, 934875505629,7736017417875,64014903727101, 529718029036659,4383372838967325, 36272047376485971,300148189354569789, 2483701419932212275] |